<!doctype html>
<html>

<head>
  <meta charset="utf-8">
  <title>无标题文档</title>
</head>
<style type="text/css">
  .content {}

  .left {
    background-color: #0F0;
    height: 100px;
    margin-right: 120px;
  }

  .right {
    width: 120px;
    background-color: #F00;
    height: 100px;
    float: right;
  }
</style>

<body>
  <div class="content">
    <div class="right">
      右
    </div>
    <div class="left">
      左
    </div>
  </div>



</body>

</html>